<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div#box {
            text-align: center;
        }
        div#box div#btn {
            margin: auto;
            width: 50px;
            height: 50px;
            line-height: 50px;
            background-color: #ddd;
            border-radius: 100%;
            color: #fff;
            cursor: pointer;
        }
    </style>
</head>
<body>
    <div id="box">
        <div id="btn">开</div>
        <img id="img" src="pic_bulboff.gif" alt="" />
    </div>
    <script>
        (function(){
            var btn = document.querySelector("#btn");
            var img = document.querySelector("#img");
            btn.onclick = function() {
                console.log("this:", this);
                //console.log(this.innerHTML);
                if(this.innerHTML == "开") {
                    img.src = "pic_bulbon.gif";
                    this.innerHTML = "关";
                    this.style.backgroundColor = "green";
                } else {
                    img.src = "pic_bulboff.gif";
                    this.innerHTML = "开";
                    this.style.backgroundColor = "#ddd";
                }
            }
        }());
    </script>
</body>
</html>